1. Field of the Invention
This invention relates to aqueous dispersion type vibration-damping coating compositions. More particularly, this invention relates to a new aqueous dispersion type vibration-damping ternary coating composition containing, as essential components thereof, (a) a polyvinyl acetate emulsion, (b) a polyethylene in finely divided particulate or emulsion state and (c) a flaky inorganic powder.
2. Description of the Prior Art
The hitherto-known methods of preventing noise and vibrations in cars, boats, buildings, etc. include the method of affixing a vibration-damping sheet or board to the wall, floor or other surfaces of the building, machine or machine component which may be a source of noise and vibrations and the method of coating such surfaces with a vibration-damping coating material. These methods have been practiced, though to a limited extent.
Such sheets and boards and coating materials are usually based on rubber or asphalt. However, while such materials may exhibit satisfactory damping performance in the neighborhood of atmospheric temperature, they have the disadvantage that said particular characteristic deteriorates considerably at reduced and elevated temperatures. Moreover, prolonged exposure to an elevated temperature results in running, sagging or blistering of the coating while the coating film may peel at low temperature. Because of these and other drawbacks, the conventional materials cannot be successfully applied to areas involving prolonged exposure to high temperature, such as the engine rooms of cars and marine craft, but have found application only in limited areas of use.
Meanwhile, various vibration-damping compositions based on synthetic resin and inorganic filler components have been proposed in recent years. While these materials are superior to rubber- or asphalt-based materials in durability at elevated temperature, they have one disadvantage or another as will be mentioned below.
Thus, Japanese Patent Publication No. 36492/1978 describes a vibration-damping material composed of vinyl polymer, cement and spherical sand but this material is not only inadequate in vibration-damping characteristic but has a limited durability and, therefore, is not satisfactory for practical use.
In Japanese Patent Application Laid-Open No. 52545/1978, there is disclosed a vibration-damping coating composition comprising an aqueous emulsion of a high polymer having a secondary transition point between 0.degree. and 100.degree. C., a flaky inorganic filler and a granular inorganic filler but while this coating material displays a satisfactory vibration-damping characteristic in a narrow temperature range in the vicinity of the secondary transition point, it has the disadvantage that, outside of that range, it offers only a poor vibration-damping performance.
Japanese Patent Application Laid-Open No. 133238/1978 and No. 133239/1978 each discloses a vibration-damping coating composition comprising incinerator ash, mica, short staples of organic or inorganic fiber and a synthetic resin or rubber emulsion. Although these compositions have the advantage of low product cost, they are low in vibration-damping quality and have poor resistance to water.
The coating material made up of a resin or rubber emulsion, mica powder and siliceous sand as described in Japanese Patent Application Laid-Open No. 32538/1979 and the coating material comprising a water-soluble or dispersible resin, a sludge recovered from a phosphate process, and a filler as disclosed in Japanese Patent Application Laid-Open No. 36341/1979 are also disadvantageous in that the temperature range ensuring a satisfactory vibration-damping performance is narrow.
Thus, just like the vibration-damping materials based on asphalt or rubber, the conventional damping compositions based on synthetic resin and inorganic filler are invariably unsatisfactory in that a satisfactory damping performance is obtainable only in a limited temperature range.